1. Field of the Invention
The present invention relates to bar stock supports in general and more particularly to a novel bar stock support that has a self-adjusting resilient member which is able to support bar stock of differing diameters and differing transverse cross-sectional shapes.
2. Background Art
Many automatic and manual machine tools are of the type in which the feed material is a metal bar, or bar stock, of a length considerably greater than the parts to be produced from it. Since the manufacturing operation takes place at one end of the bar stock while it is rotating clamped in a chuck mechanism, it is necessary, of course, that the entire length of stock rotate. Typically, the stock is fed to the chuck though a cylindrical spindle in the headstock of the machine tool, and while the inside diameter of the spindle may be such that it may closely fit the outside diameter of the largest bar stock to be used, it is not practical to change headstocks when bar stock of other diameters is to be used. When smaller bar stock is held in the chuck mechanism and rotated, the bar stock within the spindle tends to whip out of concentric rotation and the resulting whipping can cause poor surface finish on the machined parts, can create undesirable noise, and can cause poor control of the machining operation. These problems may exist even with whip control guides placed near the inlet end of the spindle and are aggravated by any nonuniformity of the bar stock.
The conventional method of reducing whipping of bar stock in the spindle of a machine tool is to provide a cylindrical "filler tube" or "spindle liner" for each size of bar stock to be used. This spindle liner has an outer diameter equal to that of the inner diameter of the spindle and an inner diameter approximating that of the nominal outside diameter of the bar stock, in order to concentrically fill the annular space between the bar stock and the spindle. While this arrangement is satisfactory for some applications, in some cases it does not compensate sufficiently for the difference in diameters between the bar stock and the spindle and/or for nonuniformities in the bar stock, and some whipping or vibration may be experienced nevertheless. In all cases, providing spindle liners for a large number of bar stock sizes is expensive.
Additionally, working in tandem with the machine tool is a bar feeding or support device which holds and guides the bar stock to the inlet end of the headstock of the machine tool. Because the bar stock is rotating within the feeder, there is similar further aggravation of the problems discussed above with reference to headstock spindles. Such bar stock feeders may be of the oil-feed type, in which case the bar stock is reasonably well supported and thus the above problems may be somewhat minimized. Typically, however, because of a substantial cost differential, the feeder is of the pneumatic type, in which case, the above problems fully exist.
Attempts have been made to address the problem of supporting rotating bar stock without resort to the use of a separate spindle liner for each size of bar stock. One approach is described in U.S. Pat. Nos. 1,786,876 and 1,935,999 to K. Tessky. These show various configurations of metal springs inserted in the tube of a bar stock feeder. Another approach is described in U.S. Pat. No. 4,058,036 to Austin and in U.S. Pat. No. 4,149,437 to Winberg et als. Each of the latter patents shows spindle or feeder tube support devices which have hinged, self-adjusting members disposed within a tube, which members apply pressure to, and thereby concentrically support, a bar stock inserted therein over a range of bar stock sizes. Since neither of these approaches is known to be in general use, it may be assumed that each has inherent performance and/or cost disadvantages.
Accordingly, it is a principal object of the present invention to provide a self-adjusting bar stock support to minimize whipping and other undesirable radial or lateral motion of the bar stock.
It is another object of the present invention to provide a self-adjusting bar stock support which can accommodate different diameter bar stock, bar stock of different transverse cross-sectional shapes, and bar stock having nonuniformities, all with one size support.
It is another object of the present invention to provide a self-adjusting bar stock support which is economical and of simple manufacture.
Other objects of the present invention will in part be apparent and will in part appear in the following description.